Ultrasonic elevator door safety system

ABSTRACT

Ultrasonic waves may be emitted from a transmitter/receiver sonic transducer, or separate transmitter working with a separate receiver, directly or reflected into the opening between doors of an elevator; responses reflected from objects or passengers between the doors which are received within a window of response are utilized to create a door reversal signal. The ultrasonic waves may be shaped into a curtain or sheet by means of a hyperbolic reflector opening downwardly toward the doors. To equalize time of travel for sound waves emanating from a single source on one side to all parts of the door opening, the reflector may also have a parabolic shape. The sound waves may be emitted in a cylindrical pattern to accommodate elevators having circular doors. Multiple reflectors may include a convex reflector to spread the sound waves vertically.

TECHNICAL FIELD

This invention relates to using ultrasonic waves to sense the presenceof objects in the path of elevator doors.

BACKGROUND ART

In typical elevator systems known to the prior art, one type of elevatorsafety shoe comprises a mechanical arm that moves on a pivot in responseto mechanical force imparted to it as a consequence of the door closingagainst an object, or due to a passenger hitting the shoe. The typicalsafety shoe is prone to excessive wear and frequent maladjustment due tothe mechanical shock required to operate it. This disadvantage isovercome in optical elevator door safety systems which have a pluralityof light beams transmitted across the door opening. In such a system,the only force imparted to the door is the deceleration/accelerationforce to reverse door direction. Typically, the transmitters andreceivers of optical safety systems are physically attached to theelevator doors, and therefore are subject to vibrations from dooroperation. Another problem with optical systems is that horizontal, lineof sight light beams cannot be used in round elevator door systems.Vertical light beams are not used because having either the transmitteror the receiver mounted in the floor area would subject the system toextremely high wear, dirt and the like. Both systems are subject tovandalism simply because the operative parts are in the vicinity of thehead and arms of the passengers.

DISCLOSURE OF INVENTION

Objects of the present invention include provision of an elevator doorsafety system which is not subject to wear and tear, which will not fallout of adjustment, which is not prone to vandalism and which can be usedon circular elevator doors. Other objects include provision of anelevator door safety system which is of relatively low cost, has fewparts and is very adaptable to a wide variety of elevator door systems.

According to the present invention, sound waves are emitted into thearea between opening elevator doors, and return waves received fromreflections within a window of response provide a signal indication ofan object or passenger being within the path of the door, which can beused for a door reversal signal. According to the invention further, thepattern of emitted and received sound waves may be confined to a curtainor sheet pattern by means of a hyperbolic reflector; the reflector mayalso be parabolic in the between-door dimension so as to provideuniformity of distance across the entire curtain or sheet to simplifycontrol over the sensitivity window. According further to the invention,the sound waves may be emitted from one transducer and return wavesreceived at another, or, the same transducer may be used for both. Instill further accord with the invention, timing for the window ofsensitivity may be effected by means of dedicated hardware or by meansof simple software routines which may be implemented in computersotherwise utilized to control the doors and/or other elevator carfunctions.

Other objects, features and advantages of the present invention willbecome more apparent in the light of the following detailed descriptionof exemplary embodiments thereof, as illustrated in the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified schematic block diagram of a simple embodiment ofthe present invention.

FIG. 2 is a time diagram illustrating the embodiment of FIG. 1.

FIG. 3 is a logic flow chart of a simple door reversal routine which maybe used in place of much of the hardware of FIG. 1.

FIG. 4 is a simple perspective view of a circular elevator door systemwith which the present invention may be used.

FIG. 5 is a simplified diagram of another embodiment of the presentinvention.

FIG. 6 is a side elevation view of a sonic reflector which may be usedin the embodiments of FIGS. 4 and 5.

FIG. 7 is a section side elevation view taken on the line 7--7 of FIG.6.

FIG. 8 is a top plan view of the sonic reflector illustrated in FIGS. 6and 7.

FIG. 9 is a simplified diagram of another embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to FIG. 1, an elevator 11 has a pair of doors 12, 13 whichare shown in an open position, the opening 14 between which must bemonitored to determine whether there are objects or passengers in thepath of the doors 12, 13 (the space between the doors through which thedoors move as they open and close) so as to not injure passengers,objects or doors in normal operation. According to the invention, asonic transmitter 17 emits sound waves from a point above the opening 14downwardly and any reflections from generally horizontal surfaces willbe received by a sonic receiver 18 which is similarly disposed above theelevator door opening 14. To avoid sensing the tops of the elevatordoors 12, 13 and the floor of the elevator 11, the system is onlyresponsive to return waves which have a timing with respect to thetransmitted wave indicative of being within a response window 19. Inthis example, it is assumed that the elevator door opening is two metershigh, and a dead band of 15 centimeters is provided at the top and thebottom of the elevator door opening 14. In one example, the sound wavesare emitted at 120 Kilohertz, in response to an oscillator 22. While theoscillator 22 runs continuously, an AND gate 23 controls the duration ofthe pulse from the transmitter 17, whereby the system can listen forechoes after each transmitted pulse. The AND gate 23 is controlled by abistable device 24 which in turn is set and reset in response to signalsindicating times related to the initiation and termination of eachpulse. The receiver will respond to any echoes, but an AND gate 25 willcause the system to respond only to reflections which occur within theresponse window 19. The AND gate 25 is in turn controlled by a bistabledevice 26 which is set at a point in time relative to the transmittedpulse which is timed to be the beginning of the response window for theleading edge of the transmitted pulse and which is reset at a timecorresponding to the end of the response window for a reflection of thetail end of the transmitted pulse, all as is illustrated in the timingdiagram of FIG. 2.

The timing and frequency of the sonic wave are selected to accommodatethe 15 centimeter dead zone at the top and bottom of the elevator dooropening 14. The pulse must be of less spatial extent than this deadzone, and the pulse should have sufficient alternating content tofacilitate reliable reflection tuning. For a pulse having a spatialextent of 12 centimeters, with the speed of sound being approximately240 meters per second, the temporal width of the pulse would be about0.5 milliseconds. To have 60 cycles in each pulse requires 120Kilohertz. The time required for the leading edge of the pulse to reachthe beginning of the response window (that is, to traverse the 15centimeter dead zone) is 0.625 milliseconds. Similarly, any return wavefrom exactly the interface of the dead zone will take 0.625 millisecondsto traverse the distance between the edge of the response window to thereceiver 12. On the other hand, the trailing edge of the transmittedwave will take one-half millisecond longer to reach the beginning of theresponse window 19, which is 1.125 milliseconds. Thus, the total time,for the trailing edge of the pulse to reach the beginning of theresponse window 19 and a wave reflected therefrom to return to thereceiver, is 1.75 milliseconds. Thus, the beginning of the responsewindow is taken to be 1.75 milliseconds from the start of the pulse. Forthe leading edge of the pulse to reach the bottom of the response window(a distance of 1.85 meters) requires 7.708 milliseconds; the trailingedge takes another half millisecond, which is 8.208 milliseconds. Anyreflection requires 7.708 milliseconds so that the total time from thebeginning of the transmitted pulse to the last time when a reflection atthe lower edge of the response window 19 could reach the receiver 18, ifreflected from the trailing edge of the pulse, requires 15.916milliseconds.

In FIG. 1, the oscillator 22 feeds the 120 Kilohertz signal to a 13stage binary counter 29. At 120 Kilohertz, each count of the counter 29is 8.3 microseconds. Decoding the counts within the counter thereforeprovides indications of the time. The counter is reset (reestablished ata zero count) by the same signal on a line 30 that sets the bistabledevice 24 to enable transmitting the pulse into the elevator dooropening. Therefore, the counts are indicative of time elapsed since thestart of the transmitted pulse.

A first detector 31 detects a count of 60 which indicates an elapsedtime of 0.5 milliseconds from the start of the pulse. This provides thesignal to reset the bistable device 24 so that the gate 23 is no longerenabled, thereby terminating the transmitted pulse, as seen in FIG. 2.Next, a detector 32, which sets the bistable device 26, detects a countof 210, 1.75 milliseconds after the start of the transmitted pulse (FIG.2), thereby enabling the AND gate 25 to be responsive to the upper edgeof the response window. A detector 33 detects a count of 1908 and resetsthe bistable device 26, thereby rendering the AND gate no longerresponsive to the receiver 18 at the far end of the response window,15.9 milliseconds after the start of the pulse (FIG. 2). Finally, adetector 34 detects a count of 2424 which provides a signal on the line30 to again reset the counter and to set the bistable 24 so the AND gate23 will again pass 120 Kilohertz signals through to the transmitter 17.The result is that there is a new cycle every 20.2 milliseconds (FIG.2). The detectors 31-34 may simply be an array of gates so as to sensestages that are on and stages that are off. For instance, the gate 31responds to the third through seventh stages from lowest order being onand the remaining stages being off, so as to detect a count of 60. Thedetector 32 responds to the second, fifth, seventh and eighth stagesbeing on and the remainder being off, to achieve a count of 210. Thedetector 33 responds to the third through seventh and ninth througheleventh stages being on and the remainder being off, to sense a countof 1908, and the detector 34 responds to all of the fourth throughseventh, ninth and twelfth stages being on and the rest off, to sense acount of 2424. Note that when the doors are closed, the reflectionstherefrom are above the window.

The exact timing of the response window and the choice of frequency, aswell as the details of implementing apparatus which will provide for theemission of ultrasonic waves into the elevator door opening and respondonly to echoes received within the opening itself, as described, ofwhich FIG. 1 is merely an example, can be varied to suit any particularimplementation of the present invention. Instead of using a dedicatedcounter 29 and the detectors 31-34, the window may be created in asimple fashion by means of a door reversal routine illustrated in FIG.3. This may be performed in any micro or other computer which isutilized to provide control to the elevator, such as an elevator doorcontrol computer or an elevator car computer.

In FIG. 3, the door reversal routine is reached through an entry point37 and a first test 38 determines if initiation has occurred as yet, ornot. Initially, it will not have, so a negative result of test 38 willreach a step 39 which will reset the counter (a counter functionimplemented in the microcomputer) a step 40 which sets the transmitter,to enable the pulse to begin, and a step 41 which sets an initiationflag so that the next pass through the subroutine need not necessarilypass through these steps. Then other parts of the program are revertedto through a return point 42. At some point later in time, the doorreversal routine is again reached through the entry point 37 and thistime the test 38 is affirmative reaching a test 45 to determine if thecounter has reached a count of 2424, or not. Initially, it will nothave, so a test 46 is reached to determine if a count has reached 1908,or not. Initially, this test is negative reaching a test 47 to determineif the count has reached 210. At first it will not, so a negative resultof test 47 reaches a test 48 to see if the count has reached 60, or not.In the first few passes, test 48 will be negative so that other parts ofthe program are reverted to through the return point 42. Eventually, thecount will reach 60 so an affirmative result of the test 48 will reach astep 51 which resets the transmitter, thus ending the transmitted pulse.In subsequent passes through the routine of FIG. 3, test 38 will beaffirmative, tests 45-47 will be negative, and test 48 will beaffirmative and will continue to reset the transmitter (equivalent toresetting the bistable 24) redundantly, in a manner that does no harm.At some point in time, the count will have reached 210 so that anaffirmative result of test 47 will reach a step 52 to set the window(equivalent to setting the bistable 26 in FIG. 1). Thereafter, in eachpass through the routine of FIG. 3, this will be repeated, redundantly,but harmlessly. In a similar fashion when the count reaches 1908, anaffirmative result of test 46 will reach a step 53 to reset the window(equivalent to resetting the bistable 26 in FIG. 1). In subsequentpasses through FIG. 3, an affirmative result of test 46 will redundantlybut harmlessly cause step 53 to continuously reset the window.Eventually, the count in the counter will reach 2424 so an affirmativeresult of test 45 will reach the step 39 to again reset the counter, thestep 40 to set the transmitter, and the step 41 to redundantly set theinitiation (which normally has to be set only once each time that thecomputer is powered up). Thus, an affirmative result of test 45 starts anew cycle.

In FIG. 3, the tests 45-48 are identified with individual counts whichrelate to the 60 cycles of 120 Kilohertz and the particular windowdescribed with respect to FIG. 1 hereinbefore. One of the advantages ofthe present invention is that it is extremely versatile. Obviously, thetests 45-48 can be made against values set in registers, which valuescan be changed as desired so as to alter the manner in which the systemwill operate, particularly allowing the tailoring of the window and theoverall cycle time for any desired installation. In any event, thecounts referred to in tests 45-48, as well as in the detectors 31-34 areexemplary, simply to present an illustration of the invention.

Referring now to FIG. 4, another advantage of the present invention isthat it is easily used with an elevator 56 which has circular doors 57,58, which may be as described in a commonly owned copending U.S. patentapplication entitled "Elevator Door System", Ser. No. 08/146,667, filedNov. 1, 1993. Above an opening 59 between the doors 57, 58 is a sonictransceiver (transmitter/receiver) 60 and a reflector 61. As illustratedin a simplified schematic form in FIG. 5, the transceiver 60 emits sonicwaves horizontally, and these waves are reflected in a verticaldirection by a reflector 61, which is shown only simplistically in FIG.5. In FIG. 5, the elevator 62 has doors 63, 64 which may be eitherstraight or curved, the reflector 61 being able to serve in either case.Because of the nature of sound waves (not very directional) and becauseof the nature of the opening, such as the opening 59 in FIG. 4 of anelevator 56 with circular doors 57, 58, sound waves may be used inaccordance with the invention in a generally non-directed fashion byvirtue of a flat reflector 61. On the other hand, if desired, the soundwaves may be reflected into a reflector 61 which has a flat crosssection (in and out of the page as seen in FIG. 5) but which,longitudinally, has a parabolic shape (as seen in FIG. 5) so as to causethe distance of transmission and reception from and to the transceiver60 to be the same at the near side of the elevator door opening 65 as atthe far side thereof. On the other hand, in order to avoid inadvertenttriggering of the door reversal system, such as may occur from theinside of a very crowded elevator, it may be desirable to provide thesonic response in the form of a curtain or sheet, which would have avery narrow expanse front to back (as seen in FIG. 5). This may beachieved by utilizing a reflector 66 (FIG. 6) which has a hyperboliccamber as viewed from the transceiver 60, and as seen in FIG. 6. Just asis true in the case of optical waves upon a hyperbolic reflector, all ofthe waves become parallel (and thus vertical) in a system such as FIG. 5with the reflector 66 of FIG. 6. The reflector of FIG. 6, iflongitudinally hyperbolic, will be as shown in FIG. 7. The reflector ofFIGS. 6 and 7 is assumed to have a generally circular axis in ahorizontal plane, as is illustrated in FIG. 8. This facilitates its usewith the circular door of FIG. 4.

In FIG. 5, the included angle of sonic transmission from the transceiver60 in order to fill the opening 65 between the doors, is about 40°. Onetype of transducer has a conical transmit/receive pattern with anincluded angle of about 7°. If such a device is used in an embodiment asillustrated in FIG. 5, five or six such devices might be employed, orthe transceiver 60 could be moved to the left as seen in FIG. 5 so as toallow use of a lesser angle. On the other hand, a single device with a7° conical pattern might be utilized with a convex reflector 68 as isillustrated in FIG. 9 so as to create a virtual image sufficientlydistant from the reflector 61 so as to fill the reflector 61 with a 7°cone. The reflector 68 is preferably cylindrical (rather than spherical)so as to spread the beam vertically while retaining the 7° anglehorizontally.

Instead of using a reflector 66 (FIG. 8) having a generally circularaxis, a plurality of transceivers may be disposed along the circle ofthe elevator door path, each transceiver having a hyperbolic shape so asto create a sheet of sound shaped like the surface of a rightcylindrical polygon. Similarly, other combinations of transceivers andreflectors may be selected to suit any desired use of the presentinvention. However, for a simple system of gating as shown, a horizontalwave front in the doorway is preferred, to cause the response window tohave the same timing across the entire doorway. Although two-doorsystems are used for example herein, the term "doors" includes a singledoor herein. The invention may be used with doors of curvilinear crosssection other than a circle, and doors of other shapes, such aspolygonal. Reflectors may be made of metal, but hard plastic ispreferred. The transceiver herein may be a transmitter and separatereceiver as shown in FIG. 1, a transmitter/receiver as shown in FIG. 5,or multiple transmitters, receivers or transmitter/receivers, with orwithout one or more reflectors.

Thus, although the invention has been shown and described with respectto exemplary embodiments thereof, it should be understood by thoseskilled in the art that the foregoing and various other changes,omissions and additions may be made therein and thereto, withoutdeparting from the spirit and scope of the invention.

We claim:
 1. An elevator door safety system for detecting objects and/orpassengers in a door opening space through which said doors pass as theyopen and close, comprising:a transceiver including a reflector havinghyperbolic camber with an elongated focal line above said space fortransmitting ultrasonic waves into said space and for receivingultrasonic waves reflected back to said transceiver from within saidspace; and means for generating a door reversal signal in response toultrasonic waves received at said transceiver within a predeterminedrange of time from the initiation of transmission of said ultrasonicwaves.
 2. An elevator door safety system according to claim 1 whereinsaid transceiver transmits an ultrasonic pulse into said space.
 3. Anelevator door safety system according to claim 2 wherein said pulse isof about 0.5 milliseconds duration.
 4. An elevator door safety systemaccording to claim 1 wherein said reflector is mounted above said spaceand said predetermined range of time is selected to exclude reflectionsfrom the top of the doors and from the floor of the elevator.
 5. Anelevator door safety system for detecting objects and/or passengers in aplanar door opening space through which said doors pass as they open andclose, comprising:a transceiver including a reflector having hyperboliccamber with a parabolic focal line in the same plane as and above saidspace for transmitting ultrasonic waves into said space and forreceiving ultrasonic waves reflected back to said transceiver fromwithin said space; and means for generating a door reversal signal inresponse to ultrasonic waves received at said transceiver within apredetermined range of time from the initiation of transmission of saidultrasonic waves.
 6. An elevator door safety system for detectingobjects and/or passengers in the door opening space through which saiddoors pass as they open and close, wherein said space has a curvilinearhorizontal cross section, comprising:a transceiver including a reflectorhaving a hyperbolic camber and a curvilinear focal line in an extensionof and above said space for transmitting ultrasonic waves into saidspace and for receiving ultrasonic waves reflected back to saidtransceiver from within said space; and means for generating a doorreversal signal in response to ultrasonic waves received at saidtransceiver within a predetermined range of time from the initiation oftransmission of said ultrasonic waves.
 7. An elevator door safety systemaccording to claim 6 wherein said space is in the shape of a portion ofthe curved surface of a right cylinder and said transceiver includes areflector having a hyperbolic camber and a circular focal line in anextension of and above said space.
 8. An elevator door safety system fordetecting objects and/or passengers in the door opening space throughwhich said doors pass as they open and close, wherein said space has acurvilinear horizontal cross section, comprising:a transceiver includinga reflector having a hyperbolic camber and a focal line which ishorizontally curvilinear and vertically parabolic in an extension of andabove said space for transmitting ultrasonic waves into said space andfor receiving ultrasonic waves reflected back to said transceiver fromwithin said space; and means for generating a door reversal signal inresponse to ultrasonic waves received at said transceiver within apredetermined range of time from the initiation of transmission of saidultrasonic waves.
 9. An elevator door safety system according to claim 8wherein said space is in the shape of a portion of the curved surface ofa right cylinder and said transceiver includes a reflector having ahyperbolic camber and a focal line which is horizontally curvilinear andvertically parabolic in an extension of and above said space.
 10. Anelevator door safety system according to claim 1 wherein saidtransceiver comprises a transmitting transducer and a receivingtransducer.
 11. An elevator door safety system according to claim 1wherein said transceiver comprises a transducer which both transmits andreceives.
 12. An elevator door safety system according to claim 11wherein said transceiver consists of a single transducer which bothtransmits and receives.
 13. An elevator door safety system according toclaim 5 wherein said transceiver includes a plurality of reflectors. 14.An elevator door safety system according to claim 13 wherein saidtransceiver includes a plurality of reflectors in series with eachother.
 15. An elevator door safety system according to claim 13 whereinone of said reflectors has a convex cylindrical shape disposed to spreadsaid sound waves vertically.